Method and apparatus for LBT failure detection

ABSTRACT

A method for LBT failure detection performed by a UE is provided. The method includes: receiving, by a MAC entity of the UE, an LBT failure indication from a lower layer for all UL transmissions; increasing an LBT failure counter when the MAC entity receives the LBT failure indication; determining an LBT failure event occurs when the LBT failure counter is greater than or equal to a threshold; and resetting the LBT failure counter after the MAC entity has not received the LBT failure indication for a time period.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of and priority to aprovisional U.S. Patent Application Ser. No. 62/790,099, filed on Jan.9, 2019, entitled “Lower Layer Indications for LBT Results,”(hereinafter referred to as “US76297 application”). The disclosure ofthe US76297 application is hereby incorporated fully by reference intothe present application.

FIELD

The present disclosure generally relates to wireless communication, andmore particularly, to Listen-Before-Talk (LBT) failure indication andLBT failure event determination in the next generation wirelesscommunication networks.

BACKGROUND

Various efforts have been made to improve different aspects of wirelesscommunications, such as data rate, latency, reliability and mobility,for the next generation (e.g., fifth generation (5G) New Radio (NR))wireless communication systems. LBT is a mechanism by which a wirelessdevice applies Clear Channel Assessment (CCA) before using the channel.The 3rd Generation Partnership Project (3GPP) specifies a conservativeLBT scheme similar to that used by Wi-Fi nodes to ensure coexistence ofLicensed Assisted Access (LAA) with Wi-Fi. LAA uses carrier aggregationin downlink transmission to combine LTE in an unlicensed spectrum (e.g.,5 GHz) with LTE in a licensed band. In NR, LBT may be required prior toany transmission when operating on an unlicensed spectrum. There is aneed in the industry for an improved and efficient mechanism for a UE tohandle LBT failure that may take place in the physical layer.

SUMMARY

The present disclosure is directed to a method for LBT failure detectionperformed by a UE in the next generation wireless communicationnetworks.

According to an aspect of the present disclosure, a UE is provided. TheUE includes one or more non-transitory computer-readable media havingcomputer-executable instructions embodied thereon and at least oneprocessor coupled to the one or more non-transitory computer-readablemedia. The at least one processor is configured to execute thecomputer-executable instructions to: receive, by a Medium Access Control(MAC) entity of the UE, an LBT failure indication from a lower layer forall UL transmissions; increase an LBT failure counter when the MACentity receives the LBT failure indication; determine an LBT failureevent occurs when the LBT failure counter is greater than or equal to athreshold; and reset the LBT failure counter after the MAC entity hasnot received the LBT failure indication for a time period.

According to another aspect of the present disclosure, a method for LBTfailure detection performed by a UE is provided. The method includes:receiving, by a MAC entity of the UE, an LBT failure indication from alower layer for all UL transmissions; increasing an LBT failure counterwhen the MAC entity receives the LBT failure indication; determining anLBT failure event occurs when the LBT failure counter is greater than orequal to a threshold; and resetting the LBT failure counter after theMAC entity has not received the LBT failure indication for a timeperiod.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the example disclosure are best understood from the followingdetailed description when read with the accompanying figures. Variousfeatures are not drawn to scale. Dimensions of various features may bearbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a flowchart of an example method for LBT failure detectionperformed by a UE, according to an example implementation of the presentapplication.

FIG. 2 is a flowchart of an example method for updating an LBT failurecounter performed by a UE, according to an example implementation of thepresent application.

FIG. 3 is a flowchart of an example method performed by a UE afterdetermining an LBT failure event occurs, according to an exampleimplementation of the present application.

FIG. 4 is a flowchart of an example method performed by a UE when an LBTfailure problem is indicated to an upper layer, according to an exampleimplementation of the present application.

FIG. 5 is a block diagram illustrating a node for wireless communicationaccording to various aspects of the present application.

DETAILED DESCRIPTION

The following description contains specific information pertaining toexample implementations in the present disclosure. The drawings in thepresent disclosure and their accompanying detailed description aredirected to merely example implementations. However, the presentdisclosure is not limited to merely these example implementations. Othervariations and implementations of the present disclosure will occur tothose skilled in the art. Unless noted otherwise, like or correspondingelements among the figures may be indicated by like or correspondingreference numerals. Moreover, the drawings and illustrations in thepresent disclosure are generally not to scale, and are not intended tocorrespond to actual relative dimensions.

For the purpose of consistency and ease of understanding, like featuresmay be identified (although, in some examples, not shown) by the samenumerals in the example figures. However, the features in differentimplementations may be differed in other respects, and thus shall not benarrowly confined to what is shown in the figures.

The description uses the phrases “in one implementation,” or “in someimplementations,” which may each refer to one or more of the same ordifferent implementations. The term “coupled” is defined as connected,whether directly or indirectly through intervening components, and isnot necessarily limited to physical connections. The term “comprising,”when utilized, means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in theso-described combination, group, series and the equivalent. Theexpression “at least one of A, B and C” or “at least one of thefollowing: A, B and C” means “only A, or only B, or only C, or anycombination of A, B and C.”

Additionally, for the purposes of explanation and non-limitation,specific details, such as functional entities, techniques, protocols,standard, and the like are set forth for providing an understanding ofthe described technology. In other examples, detailed description ofwell-known methods, technologies, systems, architectures, and the likeare omitted so as not to obscure the description with unnecessarydetails.

Persons skilled in the art will immediately recognize that any networkfunction(s) or algorithm(s) described in the present disclosure may beimplemented by hardware, software or a combination of software andhardware. Described functions may correspond to modules which may besoftware, hardware, firmware, or any combination thereof. The softwareimplementation may comprise computer executable instructions stored oncomputer readable medium such as memory or other type of storagedevices. For example, one or more microprocessors or general-purposecomputers with communication processing capability may be programmedwith corresponding executable instructions and carry out the describednetwork function(s) or algorithm(s). The microprocessors orgeneral-purpose computers may be formed of Applications SpecificIntegrated Circuitry (ASIC), programmable logic arrays, and/or using oneor more Digital Signal Processor (DSPs). Although some of the exampleimplementations described in this specification are oriented to softwareinstalled and executing on computer hardware, nevertheless, alternativeexample implementations implemented as firmware or as hardware orcombination of hardware and software are well within the scope of thepresent disclosure.

The computer readable medium includes but is not limited to RandomAccess Memory (RAM), Read Only Memory (ROM), Erasable ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM), flash memory, Compact Disc Read-Only Memory (CD-ROM),magnetic cassettes, magnetic tape, magnetic disk storage, or any otherequivalent medium capable of storing computer-readable instructions.

A radio communication network architecture (e.g., a Long Term Evolution(LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Prosystem, or a 5G NR Radio Access Network (RAN)) typically includes atleast one base station, at least one UE, and one or more optionalnetwork elements that provide connection towards a network. The UEcommunicates with the network (e.g., a Core Network (CN), an EvolvedPacket Core (EPC) network, an Evolved Universal Terrestrial Radio Accessnetwork (E-UTRAN), a 5G Core (5GC), or an internet), through a RANestablished by one or more base stations.

It should be noted that, in the present application, a UE may include,but is not limited to, a mobile station, a mobile terminal or device, auser communication radio terminal. For example, a UE may be a portableradio equipment, which includes, but is not limited to, a mobile phone,a tablet, a wearable device, a sensor, a vehicle, or a Personal DigitalAssistant (PDA) with wireless communication capability. The UE isconfigured to receive and transmit signals over an air interface to oneor more cells in a radio access network.

A base station may be configured to provide communication servicesaccording to at least one of the following Radio Access Technologies(RATs): Worldwide Interoperability for Microwave Access (WiMAX), GlobalSystem for Mobile communications (GSM, often referred to as 2G), GSMEnhanced Data rates for GSM Evolution (EDGE) Radio Access Network(GERAN), General Packet Radio Service (GPRS), Universal MobileTelecommunication System (UMTS, often referred to as 3G) based on basicwideband-code division multiple access (W-CDMA), high-speed packetaccess (HSPA), LTE, LTE-A, eLTE (evolved LTE, e.g., LTE connected to5GC), NR (often referred to as 5G), and/or LTE-A Pro. However, the scopeof the present application should not be limited to the above-mentionedprotocols.

A base station may include, but is not limited to, a node B (NB) as inthe UMTS, an evolved node B (eNB) as in the LTE or LTE-A, a radionetwork controller (RNC) as in the UMTS, a base station controller (BSC)as in the GSM/GERAN, a ng-eNB as in an E-UTRA base station in connectionwith the 5GC, a next generation Node B (gNB) as in the 5G-RAN, and anyother apparatus capable of controlling radio communication and managingradio resources within a cell. The base station may serve one or moreUEs through a radio interface.

The base station is operable to provide radio coverage to a specificgeographical area using a plurality of cells forming the radio accessnetwork. The base station supports the operations of the cells. Eachcell is operable to provide services to at least one UE within its radiocoverage. More specifically, each cell (often referred to as a servingcell) provides services to serve one or more UEs within its radiocoverage (e.g., each cell schedules the downlink and optionally uplinkresources to at least one UE within its radio coverage for downlink andoptionally uplink packet transmissions). The base station cancommunicate with one or more UEs in the radio communication systemthrough the plurality of cells. A cell may allocate sidelink (SL)resources for supporting Proximity Service (ProSe) or Vehicle toEverything (V2X) service. Each cell may have overlapped coverage areaswith other cells.

As discussed above, the frame structure for NR is to support flexibleconfigurations for accommodating various next generation (e.g., 5G)communication requirements, such as Enhanced Mobile Broadband (eMBB),Massive Machine Type Communication (mMTC), Ultra-Reliable andLow-Latency Communication (URLLC), while fulfilling high reliability,high data rate and low latency requirements. The OrthogonalFrequency-Division Multiplexing (OFDM) technology as agreed in 3GPP mayserve as a baseline for NR waveform. The scalable OFDM numerology, suchas the adaptive sub-carrier spacing, the channel bandwidth, and theCyclic Prefix (CP) may also be used. Additionally, two coding schemesare considered for NR: (1) Low-Density Parity-Check (LDPC) code and (2)Polar Code. The coding scheme adaption may be configured based on thechannel conditions and/or the service applications.

Moreover, it is also considered that in a transmission time interval TXof a single NR frame, a downlink (DL) transmission data, a guard period,and an uplink (UL) transmission data should at least be included, wherethe respective portions of the DL transmission data, the guard period,the UL transmission data should also be configurable, for example, basedon the network dynamics of NR. In addition, sidelink resources may alsobe provided in an NR frame to support ProSe services or V2X services.

The next-generation (e.g., 5G NR) wireless network is envisioned tosupport more capacity, data, and services. A UE configured withmulti-connectivity may be connected to a Master Node (MN) as an anchorand one or more Secondary Nodes (SNs) for data delivery. Each one ofthese nodes may be formed by a cell group that includes one or morecells. For example, an MN may be formed by a Master Cell Group (MCG),and an SN may be formed by a Secondary Cell Group (SCG). In other words,for a UE configured with dual connectivity (DC), the MCG may be a set ofone or more serving cells including the Primary Cell (PCell) and zero ormore Secondary Cells (SCells), and the SCG may be a set of one or moreserving cells including the Primary Secondary Cell (PSCell) and zero ormore Secondary Cells (SCells).

As described above, the PCell may be an MCG cell that operates on theprimary frequency, in which the UE either performs the initialconnection establishment procedure or initiates the connectionreestablishment procedure. In the Multi-Radio Dual Connectivity (MR-DC)mode, the PCell may belong to the MN. The PSCell may be an SCG cell inwhich the UE performs random access (e.g., when performingreconfiguration with a sync procedure). In MR-DC, the PSCell may belongto the SN. A Special Cell (SpCell) may refer to a PCell of the MCG or aPSCell of the SCG, depending on whether the MAC entity is associatedwith the MCG or the SCG. Otherwise the term Special Cell may refer tothe PCell. A Special Cell may support a Physical Uplink Control Channel(PUCCH) transmission and contention-based Random Access, and may alwaysbe activated. Additionally, for a UE in an RRC_CONNECTED state that isnot configured with carrier aggregation/dual connectivity (CA/DC), theUE may communicate with only one serving cell which may be the primarycell. Conversely, for a UE in the RRC_CONNECTED state that is configuredwith CA/DC, a set of serving cells including the special cell(s) and allof the secondary cells may communicate with the UE.

In addition, the terms “system” and “network” herein may be usedinterchangeably. The term “and/or” herein is only an associationrelationship for describing associated objects, and represents thatthree relationships may exist. For example, A and/or B may indicatethat: A exists alone, A and B exist at the same time, or B exists alone.In addition, the character “I” herein generally represents that theformer and latter associated objects are in an “or” relationship.

In a Random Access (RA) procedure, two UE variables, including a counterfor preamble transmission (e.g., PREAMBLE_TRANSMISSION_COUNTER) and acounter for power ramping (e.g., PREAMBLE_POWER_RAMPING_COUNTER), may beincreased with every attempt. In NR-Unlicensed (NR-U) operations, powerramping may not be applied (e.g., the UE variablePREAMBLE_POWER_RAMPING_COUNTER does not increase) since a preamble isnot transmitted due to LBT failure. If the preamble is not transmitteddue to LBT failure, the UE may perform the random access resourceselection procedure again, and, the UE variablePREAMBLE_TRANSMISSION_COUNTER may not increase accordingly. As such, anindication of LBT failure from a physical layer to a MAC layer may berequired (e.g., to maintain the counters).

Moreover, given that a Scheduling Request (SR) counter may not beupdated depending on the LBT outcome, it may be beneficial to consideran additional mechanism where an SR procedure may be determined to beunsuccessful due to a systematic uplink LBT failure. This mechanism maybe generally applicable to other uplink transmissions for determining aradio link problem.

When operating on an unlicensed spectrum, if a UE wants to transmit apreamble, a msg3 in a 4-Step RA procedure, a msgA in a 2-Step RAprocedure, data on uplink configured grants, or an SR on a PUCCHresource, the UE may need to pass LBT first to occupy an LBT channel, asub-band, a Bandwidth Part (BWP), a carrier, or a cell. Since the RAprocedure, the SR procedure, or the transmission on configured grantsmay be mainly handled by the MAC layer, an LBT failure indication or anLBT success indication from a lower layer (that is in charge of LBTmechanism) may be required for those operations.

In one implementation, an upper layer (e.g., a MAC layer) may instruct alower layer (e.g., a PHY layer) to transmit a Random Access Preambleusing a selected Physical Random Access Channel (PRACH) occasion, acorresponding Random Access Radio Network Temporary Identifier(RA-RNTI), a preamble index (e.g., a UE variable PREAMBLE_INDEX asdescribed in Technical Standard (TS) 38.321) and a preamble receivedtarget power (e.g., a UE variable PREAMBLE_RECEIVED_TARGET_POWER asdescribed in TS 38.321). In one implementation, the upper layer (e.g.,the MAC layer) may instruct the lower layer (e.g., the PHY layer) totransmit a msgA (of a 2-step RA procedure) using a selected PRACHoccasion, an associated PUSCH resource, a corresponding RA-RNTI (ifavailable), a corresponding MSGB-RNTI (if available), a selectedpreamble index (e.g., PREAMBLE_INDEX) and a preamble received targetpower (e.g., PREAMBLE_RECEIVED_TARGET_POWER). In one implementation, theupper layer (e.g., the MAC layer) may instruct the lower layer (e.g.,the PHY layer) to transmit a msg3 (of a 4-step RA procedure) using thereceived uplink grant. In one implementation, the upper layer (e.g., theMAC layer) may instruct the lower layer (e.g., the PHY layer) to signalan SR on one valid PUCCH resource. In one implementation, the upperlayer (e.g., the MAC layer) may instruct the lower layer (e.g., the PHYlayer) to transmit UL data using configured grants which are configuredby a Radio Resource Control (RRC) layer per serving cell and per BWP.

FIG. 1 is a flowchart of an example method 100 for LBT failure detectionperformed by a UE, according to an example implementation of the presentapplication. In action 102, a MAC entity of the UE may receive an LBTfailure indication from a lower layer (e.g., a PHY layer) for all ULtransmissions. The LBT failure indication may be regardless of ULtransmission types. For example, the PHY layer may provide a common LBTfailure indication to the MAC entity when LBT fails for different ULtransmission operations. In one implementation, the PHY layer may sendan LBT failure indication to the MAC entity when the PHY layerdetermines that an LBT procedure of an UL transmission (e.g., regardlessof UL transmission types) fails. In one implementation, the PHY layermay drop the UL transmission when it determines that the LBT procedurefails.

In action 104, the UE (e.g., the MAC entity of the UE) may increase anLBT failure counter when the MAC entity receives the LBT failureindication. In one implementation, the LBT failure counter is increasedby a step value (e.g., 1) whenever the MAC entity receives the LBTfailure indication.

In action 106, the UE (e.g., the MAC entity of the UE) may determine anLBT failure event occurs when the LBT failure counter is greater than orequal to a threshold. In one implementation, the threshold may be aparameter (e.g., lbt-FailurelnstanceMaxCount) configured by aconfiguration (e.g., an RRC configuration). In one implementation, thethreshold may be broadcast in system information.

In action 108, the UE (e.g., the MAC entity of the UE) may reset the LBTfailure counter after the MAC entity has not received the LBT failureindication for a time period. In one implementation, the UE may set theLBT failure counter to an initial value (e.g., 0) when the UE resets theLBT failure counter. In one implementation, the time period may beindicated by a configurable timer (e.g., lbt-FailureDetectionTimer)configured by a configuration (e.g., an RRC configuration). In oneimplementation, the time period may be broadcast in system information.

An LBT failure may be caused by different operations or different ULtransmission types (e.g., transmission of RA preamble, msgA, msg3, SR,or UL data on configured grants). In one implementation, there may beone common LBT failure counter for all UL transmission types. In oneimplementation, when there are consecutive k1 LBT failure indications(or consistent k1 LBT failure indications) received from a lower layer(e.g., a PHY layer) regardless of the UL transmission types, a MACentity may determine an LBT failure event occurs. k1 may be the maximumnumber of consecutive LBT failure indications (or consistent LBT failureindications). For example, k1 may be a positive integer indicating thethreshold in action 106. The LBT failure event may also be referred toas a “consistent LBT failure” since the MAC entity consistently receivesthe LBT failure indication.

In one implementation, there may be multiple LBT failure counterscorresponding to different UL transmission operations, and thus theremay be different values of k1 for different UL transmission operations.In one implementation, the value of k1 for each operation may beprovided in a common signaling (e.g., an LBT configuration that providesLBT related information or parameters). In one implementation, the valueof k1 for different operations may be provided separately in differentsignaling. For example, the value of k1 for an RA procedure may beprovided in a random access related signaling (e.g., dedicated/commonRACH configuration), the value of k1 for SR may be provided in an SRrelated signaling, and the value of k1 for configured grants may beprovided in a related Configured Grant Configuration.

In one implementation, after determining that the LBT failure eventoccurs, the MAC entity may indicate an LBT failure problem to an upperlayer (e.g., an RRC layer). In one implementation, the MAC entity mayindicate the LBT failure problem and the operation that causes the LBTfailure problem to the upper layer. For example, an LBT failure causemay be used to indicate to the upper layer what kind of failure problemhappens to the MAC entity. In one implementation, the LBT failure causemay have one or more bits (e.g., 2 bits), where different values mayrepresent the different operations causing the failure. It may depend onUE's implementation whether to indicate different LBT failure causesfrom the MAC layer to the RRC layer. In one implementation, the RRClayer may receive an LBT failure problem related to the SR operationfrom the MAC layer, and the RRC layer may receive another LBT failureproblem related to the RA operation from the MAC layer, and so on.

In one implementation, the UE may use a UE variable (e.g., the LBTfailure counter in action 104), to count the number of consecutive LBTfailure indications regardless of the UL transmission types. In oneimplementation, the UE (e.g., the MAC entity of the UE) may set the LBTfailure counter to 0 in the initial state. In one implementation, the UE(e.g., the MAC entity of the UE) may increase the LBT failure counter by1 when receiving an LBT failure indication for all UL transmissions. Forexample, the UE (e.g., the MAC entity of the UE) may first increase theLBT failure counter by 1 when receiving an LBT failure indication thatis caused by an unsuccessful preamble transmission due to LBT failure.Then, the UE (e.g., the MAC entity of the UE) may again increase the LBTfailure counter by 1 when receiving another LBT failure indication thatis caused by an unsuccessful UL transmission using configured grants dueto LBT failure, and so on.

In one implementation, the threshold (e.g., the value of k1) may be afixed value or configured by the network (e.g., via dedicated signalingor via broadcasting in system information). In one implementation, ifthe threshold is not configured by the network, the UE may apply adefault value for the threshold. In one implementation, the UE may firstapply the threshold broadcast in system information and then apply a newvalue of the threshold if configured via dedicated signaling (e.g., RRCsignaling).

In one implementation, the MAC entity may consider LBT for a ULtransmission attempt as successful after the MAC entity has not receivedan LBT failure indication for a time period. In one implementation, whenthe MAC entity considers LBT for a UL transmission attempt assuccessful, the MAC entity may reset the LBT failure counter (e.g., setthe LBT failure counter to 0). In one implementation, the UE (or the MACentity of the UE) may reset the LBT failure counter when the MAC entityindicates an LBT failure problem to an upper layer (e.g., an RRC layer).In one implementation, the UE may stop the LBT failure counter when theMAC entity indicates the LBT failure problem to the upper layer.

In one implementation, the UE may reset the LBT failure counter when theUE performs a re-establishment procedure. In one implementation, the UEmay reset the LBT failure counter when the UE switches to anothercarrier, BWP, channel, or LBT unit. In one implementation, the UE mayreset the LBT failure counter when a reconfiguration is received relatedto LBT failure handling (e.g., when at least one of the time period inaction 108 and the threshold in action 106 is reconfigured). In oneimplementation, the UE may reset the LBT failure counter when a reset ofthe MAC entity is requested (e.g., requested by the upper layers). Inone implementation, the UE may reset the LBT failure counter when anoperating condition changes, such as a change in the operating (orserving) LBT channel, sub-band, BWP, carrier, or cell. In oneimplementation, the UE may reset the LBT failure counter upon RRC statetransition (e.g., from the RRC_IDLE state to the RRC_CONNECTED state orfrom the RRC_INACTIVE state to the RRC_CONNECTED state).

FIG. 2 is a flowchart of an example method 200 for updating an LBTfailure counter performed by a UE, according to an exampleimplementation of the present application. In action 202, the UE mayreceive a configuration that indicates at least one of the time period(used in action 108 of method 100) and the threshold (used in action 106of method 100). The configuration may be transmitted via dedicatedsignaling (e.g., RRC signaling) or broadcast in system information. Inaction 204, the UE may perform a process for LBT failure detection thatmay be similar to method 100 shown in FIG. 1. Actions 206, 208 and 210may correspond to three possible conditions to reset the LBT failurecounter. In action 206, the UE may reset the LBT failure counter when atleast one of the time period and the threshold is reconfigured (e.g.,when the UE receives an RRC reconfiguration message that changes atleast one of the time period and the threshold). In action 208, the UEmay reset the LBT failure counter when the UE switches to another BWP.In action 210, the UE may reset the LBT failure counter when a reset ofthe MAC entity is requested. It should be noted that although actions206, 208, and 210 are delineated as separate actions represented asindependent blocks in FIG. 2, these separately delineated actions shouldnot be construed as necessarily order dependent. The order in which theactions are performed in FIG. 2, is not intended to be construed as alimitation. Moreover, one or more of the actions 206, 208, and 210 maybe omitted in some of the present implementations.

In one implementation, when an upper layer (e.g., the RRC layer)receives an LBT failure problem indication or the LBT failure eventoccurs because the LBT failure counter is greater than or equal to k1,the UE (e.g., the RRC layer of the UE) may perform at least one of thefollowing actions based on configurations or pre-defined rules: performa Radio Link Failure (RLF) recovery procedure, perform are-establishment procedure, and switch an active BWP of the UE toanother BWP or carrier. For example, when the LBT failure event occurs,the UE may switch the active UL BWP to another UL BWP. In oneimplementation, when the LBT failure event occurs, the UE may switch theactive UL BWP to another UL BWP configured with common RACH resources.In some implementations, the UE may transmit an RRC re-establishmentrequest in response to the LBT failure event. In one implementation, ifa re-establishment procedure is performed due to an LBT failure problem,the UE may transmit an RRC re-establishment request (e.g., theRRCReestablishmentRequest message) indicating a re-establishment causeas LBT failure. In one implementation, the LBT failure problemindication is common for all operations. In another implementation,there is one specific LBT failure problem indication for each operation.When the upper layer receives the LBT failure problem indication for onespecific operation, the upper layer may perform a specific action (e.g.,triggering re-establishment procedure, triggering RLF recoveryprocedure, and/or switching to another carrier/BWP) based on thespecific operation.

FIG. 3 is a flowchart of an example method 300 performed by a UE afterdetermining an LBT failure event occurs, according to an exampleimplementation of the present application. Action 106 shown in FIG. 3may be corresponding to action 106 shown in FIG. 1. After the UEdetermines the LBT failure event occurs, there may be severalimplementations for the UE to respond to such situation. In oneimplementation, the UE may perform action 302 to switch an active (UL)BWP of the UE to another (UL) BWP. In one implementation, the UE mayperform action 304, where the MAC entity of the UE may indicate an LBTfailure problem to an upper layer (e.g., the RRC layer). It should benoted that action 302 and action 304 are not construed as necessarilyorder dependent. Moreover, both of action 302 and action 304 may beoptionally performed in some of the present implementations.

In one implementation, when an upper layer (e.g., the RRC layer)receives an LBT failure problem indication or the LBT failure eventoccurs because the LBT failure counter is greater than or equal to thethreshold, the UE (e.g., the RRC layer of the UE) may transmit an LBTfailure problem report to the network. The LBT failure problem reportmay include information of which LBT channel/carrier/BWP/unit suffersfrom the LBT failure problem, or which operation suffers from the LBTfailure problem. In dual connectivity mode (or MR-DC mode), if a UEdetermines an LBT failure problem on a Primary Secondary Cell (PSCell)or a Secondary Cell Group (SCG) operating on an unlicensed spectrum, theUE may send an LBT failure problem report or an SCG failure report(including information of the LBT failure problem) to the master node(which may operate on the licensed spectrum or the unlicensed spectrum).In dual connectivity mode (or MR-DC mode), if a UE determines an LBTfailure problem on a Primary Cell (PCell) or a Master Cell Group (MCG)operating on the unlicensed spectrum, the UE may send an LBT failureproblem report or an MCG failure report (including information of theLBT failure problem) to the secondary node (which may operate onlicensed spectrum or unlicensed spectrum).

FIG. 4 is a flowchart of an example method 400 performed by a UE when anLBT failure problem is indicated to an upper layer, according to anexample implementation of the present application. Action 304 shown inFIG. 4 may be corresponding to action 304 shown in FIG. 3. After the MACentity of the UE indicates the LBT failure problem to an upper layer(e.g., the RRC layer), the UE (e.g., the RRC layer of the UE) mayperform an RLF recovery procedure in action 402. In one implementation,the UE may trigger an MCG RLF recovery procedure (e.g., action 404) whenthe LBT failure event takes place in a PCell, and the UE may trigger anSCG RLF recovery procedure (e.g., action 406) when the LBT failure eventtakes place in a PSCell. In action 404, the UE may perform are-establishment procedure by transmitting an RRC re-establishmentrequest message indicating a re-establishment cause as LBT failure whenthe LBT failure event occurs in a PCell. In action 406, the UE maytransmit, to a master node, an SCG failure report indicating the LBTfailure problem when the LBT failure event occurs in a PSCell. It shouldbe noted that action 404 and action 406 are not construed as necessarilyorder dependent. Moreover, action 404 and/or action 406 may beoptionally omitted in some of the present implementations.

In one implementation, there may be an LBT failure indication but no LBTsuccess indication. When there is no LBT success indication, there maybe an LBT success timer. In one implementation, an expiry time for theLBT success timer may correspond to the time period in action 108. Inone implementation, when the MAC entity instructs a lower layer (e.g.,the PHY layer) to start an UL transmission attempt (e.g., transmitting arandom access preamble, transmitting a msg3, transmitting a msgA,signaling an SR on one valid PUCCH resource, or transmitting UL datausing configured grants), the MAC entity may start or restart the LBTsuccess timer for each attempt. In one implementation, when the LBTsuccess timer is running and the MAC entity receives an LBT failureindication, the UE (or the MAC entity of the UE) may stop the LBTsuccess timer and consider the attempt as unsuccessful. In oneimplementation, the MAC entity may start or restart the LBT successtimer when the MAC entity receives an LBT failure indication from thelower layer. In one implementation, the MAC entity may consider theattempt as successful when the LBT success timer expires. In oneimplementation, the MAC entity may reset the LBT failure counter whenthe MAC entity considers the attempt as successful (e.g., when the LBTsuccess timer expires).

In one implementation, when the MAC entity instructs a lower layer(e.g., the PHY layer) an attempt to start an UL transmission, the MACentity may start or restart the LBT success timer for each attempt whenthe associated resource arrives. In one implementation, when the MACentity indicates/instructs the lower layer to transmit a random accesspreamble, the MAC entity may start or restart the LBT success timer inthe first symbol of the selected valid PRACH resource. In oneimplementation, when the MAC entity indicates/instructs the lower layerto signal an SR, the MAC entity may start or restart the LBT successtimer in the first symbol of the selected valid PUCCH resource for theSR. In one implementation, when the MAC entity indicates/instructs thelower layer to transmit UL data using configured grants, the MAC entitymay start or restart the LBT success timer in the first symbol of thestored uplink configured grants.

In one implementation, the UE (or the MAC entity of the UE) may start orrestart the LBT success timer when the value(s) of the LBT success timeris reconfigured by the upper layer (e.g., reconfigured by RRCsignaling). In one implementation, the UE may start or restart the LBTsuccess timer when an operating condition changes, such as a change inthe operating (or serving) LBT channel, sub-band, BWP, carrier, or cell.

In one implementation, there may be no LBT success indication, and theUE may decide whether LBT is successful or not based on whether acorresponding LBT failure indication is received or not. For example,when the MAC entity indicates/instructs the lower layer to transmit arandom access preamble, the MAC entity may consider the LBT for thisattempt as successful if the MAC layer does not receive a correspondingLBT failure indication (e.g., at the beginning of the selected validPRACH resource or at the end of the selected valid PRACH resource). Forexample, when the MAC entity indicates/instructs the lower layer tosignal an SR, the MAC entity may consider the LBT for the attempt assuccessful if the MAC entity does not receive a corresponding LBTfailure indication (e.g., at the beginning of the selected valid PUCCHresource for the SR or at the end of the selected valid PUCCH resourcefor the SR). For example, when the MAC entity indicates/instructs thelower layer to transmit UL data using configured grants, the MAC entitymay consider the LBT for the attempt as successful if the MAC layer doesnot receive a corresponding LBT failure indication at the beginning ofthe stored uplink configured grants or at the end of the stored uplinkconfigured grants.

In one implementation, there may be not only an LBT failure indicationbut also an LBT success indication. The MAC entity may increase the LBTfailure counter by 1 when receiving an LBT failure indication. In oneimplementation, the LBT success indication may be regardless of MACoperations (e.g., RACH procedure, SR procedure), and there may be acommon LBT failure counter for all MAC operations. The MAC entity maydecrease the LBT failure counter by 1 for all MAC operations whenreceiving the LBT success indication. In one implementation, there maybe different LBT failure counters for different MAC operations. The MACentity may decrease the different LBT failure counters for different MACoperations by 1 when receiving a common LBT success indication. In oneimplementation, there may be different types of LBT success indicationscorresponding to different types of MAC operations. The MAC entity maydecrease a specific LBT failure counter by 1 when receiving acorresponding LBT success indication for a specific MAC operation.

In one implementation, the MAC entity may identify which attempt areceived common LBT failure indication is associated with. In oneimplementation, the MAC entity may identify which attempt a receivedcommon LBT success indication is associated with. In one implementation,the MAC entity may identify which attempt the received common LBTfailure (or success) indication is associated with based on the timingof the resource used/selected by the attempt (e.g., the stored uplinkconfigured grant, the selected PRACH resource, or the valid PUCCHresources for an SR).

FIG. 5 is a block diagram illustrating a node for wirelesscommunication, in accordance with various aspects of the presentapplication. As shown in FIG. 5, a node 500 may include a transceiver520, a processor 528, a memory 534, one or more presentation components538, and at least one antenna 536. The node 500 may also include an RFspectrum band module, a base station (BS) communications module, anetwork communications module, and a system communications managementmodule, Input/Output (I/O) ports, I/O components, and power supply (notexplicitly shown in FIG. 5). Each of these components may be incommunication with each other, directly or indirectly, over one or morebuses 540. In one implementation, the node 500 may be a UE or a basestation that performs various functions described herein, for example,with reference to FIGS. 1 through 4.

The transceiver 520 having a transmitter 522 (e.g.,transmitting/transmission circuitry) and a receiver 524 (e.g.,receiving/reception circuitry) may be configured to transmit and/orreceive time and/or frequency resource partitioning information. In someimplementations, the transceiver 520 may be configured to transmit indifferent types of subframes and slots including, but not limited to,usable, non-usable and flexibly usable subframes and slot formats. Thetransceiver 520 may be configured to receive data and control channels.

The node 500 may include a variety of computer-readable media.Computer-readable media may be any available media that may be accessedby the node 500 and include both volatile and non-volatile media,removable and non-removable media. By way of example, and notlimitation, computer-readable media may comprise computer storage mediaand communication media. Computer storage media include both volatileand non-volatile, removable and non-removable media implemented in anymethod or technology for storage of information such ascomputer-readable instructions, data structures, program modules ordata.

Computer storage media includes RAM, ROM, EEPROM, flash memory or othermemory technology, CD-ROM, Digital Versatile Disks (DVD) or otheroptical disk storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices. Computer storage media do notcomprise a propagated data signal. Communication media typically embodycomputer-readable instructions, data structures, program modules orother data in a modulated data signal such as a carrier wave or othertransport mechanism and includes any information delivery media. Theterm “modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia include wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, RF, infrared and otherwireless media. Combinations of any of the above should also be includedwithin the scope of computer-readable media.

The memory 534 may include computer-storage media in the form ofvolatile and/or non-volatile memory. The memory 534 may be removable,non-removable, or a combination thereof. Example memory includessolid-state memory, hard drives, optical-disc drives, and etc. Asillustrated in FIG. 5, The memory 534 may store computer-readable,computer-executable instructions 532 (e.g., software codes) that areconfigured to, when executed, cause the processor 528 to perform variousfunctions described herein, for example, with reference to FIGS. 1through 4. Alternatively, the instructions 532 may not be directlyexecutable by the processor 528 but be configured to cause the node 500(e.g., when compiled and executed) to perform various functionsdescribed herein.

The processor 528 (e.g., having processing circuitry) may include anintelligent hardware device, e.g., a Central Processing Unit (CPU), amicrocontroller, an ASIC, and etc. The processor 528 may include memory.The processor 528 may process the data 530 and the instructions 532received from the memory 534, and information through the transceiver520, the base band communications module, and/or the networkcommunications module. The processor 528 may also process information tobe sent to the transceiver 520 for transmission through the antenna 536,to the network communications module for transmission to a core network.

One or more presentation components 538 presents data indications to aperson or other device. Examples of presentation components 538 mayinclude a display device, speaker, printing component, vibratingcomponent, etc.

From the above description, it is manifested that various techniques maybe used for implementing the concepts described in the presentapplication without departing from the scope of those concepts.Moreover, while the concepts have been described with specific referenceto certain implementations, a person of ordinary skill in the art mayrecognize that changes may be made in form and detail without departingfrom the scope of those concepts. As such, the described implementationsare to be considered in all respects as illustrative and notrestrictive. It should also be understood that the present applicationis not limited to the particular implementations described above, butmany rearrangements, modifications, and substitutions are possiblewithout departing from the scope of the present disclosure.

What is claimed is:
 1. A user equipment (UE) comprising: one or morenon-transitory computer-readable media having computer-executableinstructions embodied thereon; and at least one processor coupled to theone or more non-transitory computer-readable media, the at least oneprocessor is configured to execute the computer-executable instructionsto: receive, by a Medium Access Control (MAC) entity of the UE, aListen-Before-Talk (LBT) failure indication from a lower layer of the UEfor all uplink (UL) transmissions; increase an LBT failure counter whenthe MAC entity receives the LBT failure indication; determine that anLBT failure event has occurred when the LBT failure counter is greaterthan or equal to a threshold; and reset the LBT failure counter when areset of the MAC entity is requested by an upper layer of the UE.
 2. TheUE of claim 1, wherein the at least one processor is further configuredto execute the computer-executable instructions to: switch an activeBandwidth Part (BWP) of the UE to another BWP after determining that theLBT failure event has occurred.
 3. The UE of claim 1, wherein the atleast one processor is further configured to execute thecomputer-executable instructions to: indicate, by the MAC entity of theUE, to the upper layer of the UE an LBT failure problem afterdetermining that the LBT failure event has occurred.
 4. The UE of claim3, wherein the at least one processor is further configured to executethe computer-executable instructions to: perform a Radio Link Failure(RLF) recovery procedure.
 5. The UE of claim 1, wherein the at least oneprocessor is further configured to execute the computer-executableinstructions to: perform a re-establishment procedure by transmitting aRadio Resource Control (RRC) re-establishment request message indicatinga re-establishment cause as LBT failure, when the LBT failure eventoccurs in a Primary Cell (PCell).
 6. The UE of claim 1, wherein the atleast one processor is further configured to execute thecomputer-executable instructions to: transmit, to a master node, aSecondary Cell Group (SCG) failure report indicating the LBT failureproblem when the LBT failure event occurs in a Primary Secondary Cell(PSCell).
 7. The UE of claim 1, wherein the at least one processor isfurther configured to execute the computer-executable instructions to:receive a configuration that indicates the threshold.
 8. The UE of claim1, wherein the at least one processor is further configured to executethe computer-executable instructions to: reset the LBT failure counterwhen the threshold is reconfigured.
 9. The UE of claim 1, wherein the atleast one processor is further configured to execute thecomputer-executable instructions to: reset the LBT failure counter whenthe UE switches from an active Bandwidth Part (BWP) of the UE to anotherBWP.
 10. A method for Listen-Before-Talk (LBT) failure detectionperformed by a User Equipment (UE), the method comprising: receiving, bya Medium Access Control (MAC) entity of the UE, a Listen-Before-Talk(LBT) failure indication from a lower layer of the UE for all uplink(UL) transmissions; increasing an LBT failure counter when the MACentity receives the LBT failure indication; determining that an LBTfailure event has occurred when the LBT failure counter is greater thanor equal to a threshold; and resetting the LBT failure counter when areset of the MAC entity is requested by an upper layer of the UE. 11.The method of claim 10, further comprising: switching an activeBandwidth Part (BWP) of the UE to another BWP after determining that theLBT failure event has occurred.
 12. The method of claim 10, furthercomprising: indicating, by the MAC entity of the UE, to the upper layerof the UE an LBT failure problem after determining that the LBT failureevent has occurred.
 13. The method of claim 12, further comprising:performing a Radio Link Failure (RLF) recovery procedure.
 14. The methodof claim 10, further comprising: performing a re-establishment procedureby transmitting a Radio Resource Control (RRC) re-establishment requestmessage indicating a re-establishment cause as LBT failure, when the LBTfailure event occurs in a Primary Cell (PCell).
 15. The method of claim10, further comprising: transmitting, to a master node, a Secondary CellGroup (SCG) failure report indicating the LBT failure problem when theLBT failure event occurs in a Primary Secondary Cell (PSCell).
 16. Themethod of claim 10, further comprising: receiving a configuration thatindicates the threshold.
 17. The method of claim 10, further comprising:resetting the LBT failure counter when the threshold is reconfigured.18. The method of claim 10, further comprising: resetting the LBTfailure counter when the UE switches from an active Bandwidth Part (BWP)of the UE to another BWP.
 19. The user equipment (UE) of claim 1,wherein the at least one processor is further configured to execute thecomputer-executable instructions to: reset the LBT failure counter afterthe MAC entity has not received the LBT failure indication for a timeperiod.
 20. The method of claim 10, further comprising: resetting theLBT failure counter after the MAC entity has not received the LBTfailure indication for a time period.